Date: Thu, 30 Aug 2001 22:07:34 +0200 From: Erik Trulsson <ertr1013@student.uu.se> To: Kory Hamzeh <kory@avatar.com> Cc: Mike Meyer <mwm@mired.org>, questions@FreeBSD.ORG Subject: Re: Performance tuning results Message-ID: <20010830220733.A27037@student.uu.se> In-Reply-To: <003b01c13178$ad44fa60$14ce21c7@avatar.com> References: <15245.63001.898491.751110@guru.mired.org> <003b01c13178$ad44fa60$14ce21c7@avatar.com>
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On Thu, Aug 30, 2001 at 10:24:51AM -0700, Kory Hamzeh wrote: > > > > -----Original Message----- > > From: owner-freebsd-questions@FreeBSD.ORG > > [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Mike Meyer > > > What's interesting is that IDE write caching helped more than the > > > softupdates. > > > > Why is that interesting? Softupdates caches things in the system > > memory to try and improve performance in a reliable manner. IDE disk > > caching caches things in the disks memory without worrying about > > reliability. One would expect the more reliable mechanism to be > > slower. > > Because I assume that the system buffer cache is larger than the drive's > buffer cache. But the drive's is probably more efficient since it has access to all the internals of the drive. Eg. the real geometry of the drive (which is almost certainly different from teh geometry the drive reports to the OS/BIOS.) > > > > > If you really want the extra speed - and don't care about reliability > > - you can mount your file systems async, softupdates off. If soft > > udpates are on, the async flag to mount is quietly ignored. That > > caches data in the system memory without regard to reliability just > > like the IDE disk cache does. > > > > Why is IDE write caching less reliable than softupdates? They both basically > do the same thing: delay the write. The softupdates code takes care to order the actual writes to the drive in such a manner that the filesystem should always be in a consistent state. The drive's cache system doesn't do that. -- <Insert your favourite quote here.> Erik Trulsson ertr1013@student.uu.se To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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